1. Field
The present disclosure relates generally to telecommunications, and more particularly, to the selection of an access point in a communications system.
2. Background
In a wireless communications system, a wireless access network may be used to connect any number of access terminals to a wide area network (WAN), such as the Internet or other packet-based network. The access network is typically implemented with any number of access points distributed throughout a geographic region. Each access point is configured to provide a point of access to one or more access terminals in its vicinity. In some implementations, the access network may be confined to a relatively small geographic region using a standard protocol, such as World Interoperability for Microwave Access (WiMAX), wireless fidelity alliance (Wi-Fi Alliance), 802.11 network technology, Bluetooth technology, ultra wide band (UWB) protocol, home radio frequency (HomeRF), or the like. These type of access networks are generally referred to as wireless local area networks (WLAN) and are often found in homes, offices, buildings, and other private and public places.
As WLANs become ubiquitous, the techniques used to select a serving access point, and roam from one access point to another, have a greater impact on the quality of service experienced by the user on an access terminal. Typically, the selection process begins with a list of access points created by the access terminal. The access terminal creates this list by scanning the spectrum of channels to discover all nearby access points. This list is used by the access terminal to associate with an access point on power up, and transition from one access point to another as the access terminal moves throughout the access network.
Depending upon the particular implementation, the scan may be either passive or active. An access terminal performs a passive scan by tuning to each channel and listening for one or more beacons. This requires the access terminal to remain on each channel for a time period equal to at least the beacon signal interval period. Alternatively, access terminal may use an active scan in which it transmits a probe on each channel. However, the access terminal must still wait for a response from one or more access points on each channel. Either way, the access terminal must scan a wide spectrum of channels and spend significant processor resources to search for access points. This results in increased power consumption and reduced battery life.